1. Field of the Invention
The present invention relates to a sound field forming circuit including a first tone control circuit which variably adjusts a characteristic of a first predetermined frequency band of an audio signal, a second tone control circuit which variably adjusts a characteristic of a second predetermined frequency band of the audio signal, and first and second channels which output audio signals that are supplied from the first and second tone control circuits, respectively, and also to a sound field forming apparatus including such a sound field forming circuit.
2. Description of the Related Art
For example, a conventional sound field forming circuit which is to be mounted in an audio apparatus or the like is configured as shown in FIG. 6. An audio signal from an audio signal source (such as an AM/FM radio broadcasting, a cassette tape player, a CD (Compact Disc) player, a MD (Mini Disc) player, or a DVD (Digital Video Disc) player) is output to front and rear channels via a first tone control circuit (Tone1) and a second tone control circuit (Tone2). Audio signals from the front channel (ch1) and the rear channel (ch2) are output to respective speakers.
In this configuration, for example, a characteristic (gain) of the high-frequency band can be adjusted by the first tone control circuit, and a characteristic (gain) of the low-frequency band can be adjusted by the second tone control circuit, thereby enabling the listener to listen a desired tone range corresponding to the audio signal source.
However, such a conventional sound field forming circuit has a problem in that, even when characteristics of frequency bands can be adjusted by the first and second tone control circuits, the frequency characteristics of the front and rear channels are identical with each other and hence a deep sound field cannot be formed.
It is an object of the invention to provide a sound field forming circuit which solves the problem, and which can form a sound field that is deep and full of variety, and a sound field forming apparatus comprising such a sound field forming circuit.
In order to attain the object, the sound field forming circuit according to a first aspect of the invention comprises: a first tone control circuit which variably adjusts a characteristic of a first predetermined frequency band of an audio signal; a second tone control circuit which variably adjusts a characteristic of a second predetermined frequency band of the audio signal; first and second channels which output audio signals that are supplied from the first and second tone control circuits, respectively; a first switch portion which switchingly supplies one of an audio signal from a sound source and the audio signal output from the second tone control circuit, to the first tone control circuit; a second switch portion which switchingly supplies one of the audio signal from the sound source and the audio signal output from the first tone control circuit, to the second tone control circuit; a third switch portion which switchingly supplies one of the audio signal output from the first tone control circuit and the audio signal output from the second tone control circuit, to the first channel; and a fourth switch portion which switchingly supplies one of the audio signal output from the first tone control circuit and the audio signal output from the second tone control circuit, to the second channel.
According to the first aspect of the invention, a connection pattern of the sound field forming circuit is formed in accordance with a combination of switching of the first to fourth switches, and audio signals having a frequency characteristic corresponding to the connection pattern are output. Therefore, the circuit can provide the listener with a sound field that is deep and full of variety.
The sound field forming apparatus according to a second aspect of the invention comprises: a sound field forming circuit according to the first aspect of the invention; and controlling means for switchingly controlling the first, second, third, and fourth switches which are disposed in the sound field forming circuit, thereby forming a connection pattern of the sound field forming circuit.
According to the second aspect of the invention, the controlling means switchingly controls the first, second, third, and fourth switches, so that various connection patterns of the sound field forming circuit can be formed and audio signals having a frequency characteristic corresponding to such a connection pattern can be output. Therefore, the apparatus can provide the listener with a sound field that is deep and full of variety.
The sound field forming apparatus according to a third aspect of the invention is configured so that, in the sound field forming apparatus of the second aspect of the invention, the controlling means switchingly controls the first, second, third, and fourth switches in accordance with a command signal from an operation unit which designates the connection pattern.
According to the third aspect of the invention, the listener can set a connection pattern of the sound field forming circuit which is suitable to the taste of the listener.